Geochemical Characteristics And Origin Of Cobalt-Rich Crusts From Central Pacific Ocean

In this paper, the mineralogy, the micro-textures and the elemental geochemistry of the cobalt-rich crusts from the Central Pacific Ocean were analyzed systematically using the ICP-AES, the EPMA, and the X-ray diffraction combined with mathematical statistics such as factor analysis and cluster analysis, and so on. And then, the formation mechanism of the cobalt-rich crusts was discussed. The main conclusions of this study are:1 The types of the cobalt-rich crusts from the Central Pacific Ocean are the hydrogenous. The mineralogies of them are vernadite, iron oxyhydroxide and minor non-metal phases. Many kinds of primary and secondary structures formed in the layers of cobalt-rich crusts.2 Phosphorization changes not only the original element contents in the cobalt-rich crusts, but also the correlationships between the elements. Thus these sensitive element pairs could be used as the indicators of phosphorization. The variations of major elements in the non-phosphatized cobalt-rich crusts to the longitude, latitude in different water intervals is similare each other, and thus these can be explained by the physicochemistry bars in seawater, surface-water bio-productivity and material sources, and so on. That the change of major elements with water depth in different areas is similare, which illustrates that the regional stratification of ocean water chemistry.3 The REE contents and LREE/HREE ratios in the non-phosphatized cobalt-rich crusts take regular variations with waterdepth, while these variations could be elucidated by two processes: one is the adsorption of setting particulates in ocean column, another is the contents and behaviors of the REE in ocean. The Ce in the cobalt-rich crusts occurs as the Ce(â…£), and its enrichment is a kinetic process, thus the Ce anomalies could not used as the redox proxy of the formation environment of the cobalt-rich crusts.4 Based on the investigation into the microlayers which showing the crenulated and having the different growth rates, one interface electric double layer model was suggested to describe that the precipitation of the cobalt-rich crusts on the surfaces of the various substrates. Although the environment of them change from a early lower oxidizing condition to a higher later generally, the microenvironment alter alternatively from the higher oxygen level to the lower.